Alex Wong/Getty Images(WASHINGTON) -- President Obama said Monday he has "no patience" for reports that the Internal Revenue Service singled out conservative groups for additional scrutiny, promising accountability if allegations of political motivations at the agency turn out to be true.

"So we'll wait and see what exactly all the details and the facts are," Obama said at a news conference. "But I've got no patience with it. I will not tolerate it. And we'll make sure that we find out exactly what happened on this."

But trouble appears to be brewing for the Obama administration as allegations emerge that the IRS engaged in wide-spread targeting of conservative groups for several years, in many cases delaying the groups' applications for tax-exempt status.

"People have to be confident that they are...applying the laws in a non-partisan way," Obama said Monday.

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Since as early as 2010, IRS officials have selected organizations whose names or mission statements suggested an affiliation with conservative or tea party causes, singling them out for additional scrutiny, according to excerpts of a forthcoming Inspector General report on the practice.

The new allegations suggest that problems at the IRS might have gone on far longer than the organization first admitted Friday. And the practice appears to have been more widespread than was initially admitted.

The IRS official responsible for the unit that scrutinizes applications for tax-exempt status, Lois Lerner, apologized Friday for inappropriately targeting groups with "Tea Party" or "patriot" in their names.

"They didn't do it because of any political bias," Lerner said Friday. "It was an error in judgment and it wasn't appropriate but that's what they did."

Now, with reports showing the targeting may not have been limited to groups associated with those two phrases, conservative groups responded with fury.

"This ominous stifling of free speech can never happen again in America, and there needs to be a full accounting of who knew what, when did they know it, and who is responsible," said FreedomWorks President Matt Kibbe in a statement on Monday. "The IRS used its power to discourage and intimidate Americans from speaking out against bad policies, stifling the First Amendment right of every citizen to hold government accountable. This is the stuff of Third World Juntas, not the greatest Constitutional Republic in human history."

The IRS said the practice was not politically motivated, but was rather an effort by "front line" officials to deal with an influx of new applications for tax-exempt status that needed additional attention in order to comply with the law.

Several lawmakers are now calling for investigations into the practice.

And others, including Sen. Marco Rubio, R-Fla., and Sen. Joe Manchin, D-W.Va., have called for officials to resign for their role in the scandal.

"The actions of the IRS are unacceptable and un-American. Government agencies using their bureaucratic muscle to target Americans for their political beliefs cannot be tolerated," Manchin said in a statement. "The president must immediately condemn this attack on our values, find those individuals in his administration who are responsible and fire them."

The top Democrat in the Senate on tax issues, Chairman of the Senate Finance Committee Sen. Max Baucus, D-Mont., warned the IRS that it should be prepared for a full investigation from the committee.

"We need to get to the bottom of what happened here. I want to see all the facts. We need to know who knew what, and exactly what mistakes were made," Baucus said in a statement. "I want to review the Inspector General's report first, but the IRS should be prepared for a full investigation into this matter by the Senate Finance Committee. The IRS will now be the ones put under additional scrutiny."

Baucus says the actions by the IRS were an "intolerable" and "outrageous abuse of power and a breach of the public's trust."

Several tea party and conservative groups had complained for years that the IRS had requested onerous amounts of documentation, including donors lists, from organizations during the process of applying for tax-exempt status.

But watchdog groups who had called on the IRS to scrutinize further tax-exempt groups say the news came as a surprise.

"It had seemed if anything, that the IRS was very inactive in this arena," Lisa Gilbert, director of Public Citizen's Congress Watch, said Monday. "We raised alarm bells around that in the past."

Gilbert added that blowback from missteps by low-level employees should not prevent the IRS from cracking down on illegal political activity by these tax-exempt "social welfare" organizations.

"We're not supportive of any kind of biased methodology that looks at tax-exempt organizations. But we are very supportive of the IRS expanding their scrutiny of 501(c)4 organizations," she said.

The IG report suggests that the practice might have begun after the landmark 2010 Citizen's United vs. Federal Election Commission Supreme Court case, which was viewed as expanding the ability for nonprofit organizations to become involved in political elections.

David Bossie, executive director of Citizen's United, the organization that brought the case against the FEC, said the new information should prompt a full congressional investigation.

"The IRS clearly saw the Citizens United case as a catalyst to go after conservative groups in the lead-up to President Obama's re-election," Bossie said in a statement. "The Obama Administration's obsession of win-at-all-costs has brought Chicago-style politics to the IRS. A full and complete congressional investigation must commence immediately and those who targeted fellow Americans for pure political purposes must be held accountable under the fullest extent of the law."